1. Field of the Invention
The present invention generally relates to audio coding. More particularly, the present invention relates to a device and a method for scalable audio coding.
2. Background of the Invention
Multimedia streaming provides real-time video and audio services over a communication network, and in the last decade has become one of the primary tools for transmitting video and audio signals. Various aspects of multimedia streaming have become the focus of research and product development. One aspect is the capability of adjusting, in real time, the content or amount of multimedia data according to channel conditions, such as channel traffic or bit rate available for transmitting data over one or more communication channels. In particular, because the channel bandwidth available for transmitting multimedia data may vary over time, the content or the amount of the data transmitted may be adjusted over time accordingly to accommodate bandwidth variations, maximize the use of bandwidth, and/or minimize the impact of limited bandwidth. However, traditional coding methods are typically designed for transmitting data at a fixed bit rate and may frequently be impacted by bandwidth variations.
Fine Granularity Scalability (“FGS”) coding is a coding method allowing the transmission bit rate to vary over time. The concept of FGS makes a set of data, or at least part of that data, “scalable,” which means that data may be transmitted with varied length or in discrete portions without affecting a receiver's ability to decode the data. Due to the limitations of fixed bit-rate coding noted above and the scalability of FGS, it has become a popular option for real-time streaming applications. In particular, the Motion Picture Experts Group (“MPEG”) has adopted FGS coding and incorporated it into the MPEG-4 standard, a standard covering audio coding and decoding.
Another coding technique, scalable video coding, has recently been proposed to provide FGS features. For example, a Scalable Lossless (“SLS”) coder, which uses FGS coding approaches, has been proposed to be incorporated into MPEG standards.
However, current coding approaches, such as those of SLS coders, may be limited in accommodating bit-rate variations or low bit-rate availabilities. The quality improvement derived from employing additionally available bandwidth may be, under some circumstances, limited. There is therefore a need for improved coding techniques.